Absorbent nonwoven materials are often used for wiping spills and leakages of all kinds in industrial, service, office and home locations. The basic synthetic plastic components normally are hydrophobic and will absorb oil, fat and grease, and also to some degree water by capillary force. To reach a higher water absorption level, cellulosic pulp is often added. A variety of demands are put on nonwoven materials made for wiping purposes. An ideal wiper should be strong, absorbent, abrasion resistant and exhibit low linting. In order to replace textile wipers, which is still a major part of the market, the nonwoven wipers should further be soft and have a textile touch.
Nonwoven materials comprising mixtures of cellulosic pulp and synthetic fibres can be produced by conventional papermaking processes, see e.g. U.S. Pat. No. 4,822,452, which describes a fibrous web formed by wetlaying, the web comprising staple length natural or synthetic fibres and cellulose paper-making fibres. An associative thickener is further added to the furnish.
Hydroentangling or spunlacing is a technique introduced during the 1970'ies, see e.g. CA patent no. 841 938. The method involves forming a fibre web which is either drylaid or wetlaid, after which the fibres are entangled by means of very fine water jets under high pressure. Several rows of water jets are directed against the fibre web which is supported by a movable fabric. The entangled fibre web is then dried. The fibres that are used in the material can be synthetic or regenerated staple fibres, e.g. polyester, polyamide, polypropylene, rayon or the like, pulp fibres or mixtures of pulp fibres and staple fibres. Spunlace materials can be produced in high quality to a reasonable cost and have a high absorption capacity. They can e.g. be used as wiping material for household or industrial use, as disposable materials in medical care and hygiene articles etc.
In WO 96/02701 there is disclosed hydroentangling of a foamformed fibrous web. Foamforming is a special variant of wetlaying where the water besides fibres and chemicals also contains a surfactant which makes it possible to create foam where the fibres can be enmeshed in and between the foam bubbles. The fibres included in the fibrous web can be pulp fibres and other natural fibres and synthetic fibres.
Through e.g. EP-B-0 333 211 and EP-B-0 333 228 it is known to hydroentangle a fibre mixture in which one of the fibre components is meltblown fibres. A web of meltblown fibres is combined with another fibrous web and the combined webs are hydroentangled, or alternatively a “coform material” comprising an essentially homogeneous mixture of meltblown fibres and other fibres is airlaid on a forming fabric and subsequently hydroentangled.
Through EP-A-0 308 320 it is known to bring together a prebonded web of continuous filaments with a separately prebonded wetlaid fibrous material containing pulp fibres and staple fibres and hydroentangle together the separately formed fibrous webs to a laminate. In such a material the fibres of the different fibrous webs will not be integrated with each other since the fibres already prior to the hydroentangling are bonded to each other and only have a very limited mobility. The material will show a marked two-sidedness. The staple fibres used have a preferred length of 12 to 19 mm, but could be in the range from 9.5 mm to 51 mm.
EP-A-0 492 554 describes a nonwoven material made from continuous filaments and pulp fibers. Pulp fibers are wet laid on top of a bonded spunlaid web and the two layers are combined by hydroentanglement. As in the above case it is difficult to integrate a prebonded web of filaments with other fibers and the hydroentanglement energy required to combine the pulp fibers with the bonded spunlaid web is rather high.
WO 2005/042819 discloses a hydroentangled, well integrated composite nonwoven material, comprising a mixture of continuous filaments, synthetic staple fibres, and natural fibres, said material having a reduced two-sidedness. The synthetic staple fibres are short, having a length between 3 and 7 mm. The choice of such short staple fibres enables pulp fibres and staple fibres to be better mixed and distributed thoroughly throughout the nonwoven material. There are no thermal bonds between the filaments to ascertain that the fibres and filaments are fully mixed with each other.
WO 02/38846 discloses a hydroentangled nonwoven composite structure containing recycled synthetic fibrous material and continuous filaments. The recycled synthetic fibrous material comprises short thread elements, which are fractions of fibrous material separated from a bonded material suspended in a liquid. The continuous filaments are supplied in the form of a web, which is handled in roll form and therefore has to be bonded at least to some extent. The hydroentangled material is dried utilizing a non-compressive drying process such as through-air drying.
One problem occurring in many webs containing long filaments is that after use as a wiper for some time, segments of the filaments may come loose and rise as loops above the surface of the web material. This phenomenon is referred to as “pilling”. This may especially be a problem in web materials comprising a mixture of filaments and short fibers (shorter than about 8 mm) since these short fibers have a very limited ability to twist around and entangle with the filaments. The problem with pilling may be reduced by increasing the hydroentanglement energy, which however is disadvantageous in other aspects.